And some history:
"When there are more kids than spots in a popular school, how do you decide which kids get in?

CPS has tried to answer this question several times. In the 1990s, families enrolled in magnet programs via Super Saturday. CPS kept the enrollment locations (CPS schools) secret until the early morning on the last Saturday in January. After announcing the locations, lines formed quickly and schools accepted kids on a first-come, first-serve basis. Parents enlisted family and friends to patrol the city in cars so that the closest car could dash to the signup once revealed. Cars were manned in pairs, so that the passenger could get out and get in line without hunting for a parking spot. They communicated via pagers, walkie-talkies, and cellphones if they were lucky. There was more than a few fender benders in the process. Some families tried to guess the system, staking out schools for signs of “activity”, like building lights and cars.

Super Saturday ended sometime around 2000. For several years, parents enrolled their kids by taking a tour of the school and submitting a waiting list application up to 12 months before the first day of school. Your spot was not guaranteed however, and students were accepted partially on the basis of race and gender. Parents usually knew their result by December. Interestingly, this method was simple, straightforward and did not require waiting in line. However, due to demand from parents who wanted more control over their kids’ futures, as well as court decisions that outlawed the demographic basis of enrollment, CPS went to a first-come, first-serve enrollment around 2007. That first year, parents camped out in line for 24 hours.

To address the inherent unfairness in a totally first-come, first-serve enrollment method, CPS went to a hybrid system. Since 2011, 30% of open spots went to winners of a lottery system, with the rest still allocated via line. Families were eligible for the lottery only if their neighborhood school was underperforming."